This fact has been discovered by a group of German researchers. In the study, men with steady partners were given an oxytocin nasal spray remained far from an attractive woman, compared with men who unknowingly received a placebo.

The spray of oxytocin had no effect on single men who chose to get close to attractive women in the study.

 The results suggest that this hormone promotes fidelity in humans, said researcher Dr. René Hurlemann, University of Bonn.

The findings are consistent with previous research in mice, suggesting that the hormone plays a role in linking the couple.

In humans, oxytocin promotes bonding between mother and child, build confidence and reduce marital conflict. As early as 2012, a study found that couples with high levels of oxytocin in the early stages of their relationship were more likely to be together six months that couples with low levels of the hormone.

But until now, there was no evidence that a dose of oxytocin in a stable relationship contributed to the maintenance of the relationship.

The study included 57 heterosexual men, about half of which were in a relationship. After a dose of oxytocin or placebo, participants were presented with a researcher to which all later described as "attractive".

During the meeting, the researcher came up and walked away from the men and were asked to indicate when they thought he was a "great distance" and when I was at a distance that made them feel "uncomfortable".

The effect of oxytocin in men with family was the same regardless of whether the researcher maintained eye contact, or looked away. Oxytocin had no effect on the attitude of men towards women - whether they had received oxytocin or placebo-qualify when the girl as attractive.

In a separate experiment, the researchers found oxytocin had no effect on the distance men supported each other, or with a male researcher.

In conclusion, oxytocin can promote fidelity to incite men to keep their distance from attractive women.

If you wish more information, please read the full research paper:
"Oxytocin Modulates Social Distance between Males and Females"